I run my 2560x1600 U3011 off a GTX580 with 1.5GB memory, haven't noticed any issues. I don't usually crank up the AA though. If I was buying new, it would be a 670. $400 is a fair price on that Lightning though. Are you watercooling? Then pick up a reference model 670, and ignore the cards with custom cooling as you won't be using it.